1. Field of the Invention
This invention relates to a system for releasing and blocking telephone channels in signaling converters of a time division multiplex (TDM) system for pulse code modulation (PCM) in a terminal having at least one channel-specific "outgoing" or "incoming" signaling converter and a monitoring device with an alarm signal occurring simultaneously with faults and time-differentiated given disturbances.
2. Description of the Prior Art
Signaling converters are described in the publication "Siemens-Zeitschrift", 49 (1975) 7, pp. 466-472 and in the publication "Telcom-Report", 2 (1979), insert "Digital-Ubertragungstechnik" pp. 65-71.
A signaling converter equipment, is divided into central and peripheral portions. The channel-specific "outgoing" and "incoming" signaling converters are counted amongst the latter, the signaling converters being equipped with corresponding circuits for receiving and transmitting signals for the exchange. Among other things, the central devices contain monitoring circuits which allow internal device faults or disturbances of the incoming signals to be perceived. A response of specific monitoring functions, thereby, should lead to immediate or delayed release of seized channels as well as to the immediate blocking of unseized channels. The delayed release, for example, should bridge brief failures of the frame synchronism. Moreover, in such cases, signaling should likewise not be immediately interrupted. In those central portions in which the signals are merely time-division multiplexed, no evaluation of the signal contents is provided. In general, the signals here can only be set immediately or delayed to a specific binary value, for example the value "1". The effect on the blocking and releasing of connections, therefore, can only occur without differentiation either directly or delayed.